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April 2016

As indicated in our previous post, affordable Air Quality Index (AQI) measurements could help to establish a better view and understanding on what is really happening around you as far as Air Quality. Having a consolidated view and data provided in a consistent way by many sensors, will provide a single source of accurate indication of trends as well as historical data. Different technologies could be used to transmit data to the Cloud, low power and long range being preferred. With increasing penetration of LoRaWan, design of such sensor became feasible. After several long discussions, we have decided to create one. The main objective was a affordability. Virtual everyone should be able to afford it. At the same time, we do not want to “cut any corners” and we decided to measure all relevant parameters necessary to calculate Air Quality Index, just like the local Governments would do.

gases: NO2, SO2, CO and O3

particles condensation at PM2.5 and PM10.

The clean power was our secondary objective. After researching available energy sources, we have decided that solar power combined with good rechargeable battery was the most reliable source of energy for our project.

The prototypes are already collecting data across 3 continents, well still only 3 cities :). The product will be available soon through SensorsConnect web site. The product, collects all necessary variables required to establish Air Quality Index; In addition, temperature, humidity and GPS location are also measured. Collected measurements are sent over LoRaWan, operating in either private or public mode on European or North American bands of LoRaWan. In North American flavour, users can connect via full 64+8 mode gateway or hybrid mode gateway limited to one of the 8 sub-bands configurable via our provisioning interface. Each node will ship factory pre-calibrated and will provide a mechanism to self-calibrate in a clear Air. Configuration of measurement cycle duration, GPS mode of operation and LoRaWan specific parameters is available over LoRaWan and/or BLE (future perhaps). The GPS sensor provides location information and accurate clock for the unit. By default, GPS operates in a Mobile mode, collecting location information as often as a measurement cycle is called. In order to improve battery life, or simple if your device is mounted permanently at one location, GPS activity can be limited. SenseInAir® (SIA) can be re-configured to operate in a stationary or fixed position mode where only a single GPS lookup is performed in order to establish location and set unit’s internal Real Time Clock. However, having the Mobile GPS mode presents an interesting opportunity for Cities fully covered by LoRaWan. Driving around in an electric car (with the unit on your dash), could generate a virtual map of a region, indication AQI factors for all critical parts of the City. Areas and factories causing higher pollution could be easily identified and monitored.

The node will be ready for expansion. Optional (future) Zigbee interface and matching future firmware releases will accommodate additional sensors and turn it into a smart Zigbee/LoRaWan bridge. We are still contemplating if that makes sense, as it will obviously increase the unit cost. The SenseInAir® is based on STMicroelectronics STM32 series MCU designed for the Ultra-Low power mode of operation. During idle time, MCU and sensors together, consume below 1uA. With our carefully crafted hardware design and power saving algorithms, the SensorsConnect device can operate for a long time on a single battery charge, even when sun is not cooperating. For special cases, where solar charging is not suitable as energy source, the SenseInAir® could utilize a industrial grade Lithium battery strong enough to provide several years of maintenance free operation. As I mentioned before, an optional Bluetooth LE can help with initial provisioning and/or field provisioning of the unit, however full provisioning can also be performed over LoRaWan. Units, can also be ordered with custom configuration or pre-provisioned for one of the existing LoRaWan networks, ready to be plugged in and connect without any configuration. The default profile will connect via The Things Network. Affordable cost should allow ordinary citizens to install those units in their backyards. Cities will be able to install hundreds of units per municipality. Such array of those sensors will provide accurate map indicating changes and trends in air quality and pollution across a City. This information could be valuable for different applications, for instance, cars could be re-directed to alternate roads should the primary roads be over polluted. For areas without LoRaWan coverage BLE could be used to access the data locally from the single node. Additional sensors for SenseInAir® such as inside VOC ( Volatile Organic Compound), CO2 and radiation (alpha, beta and gamma) will be available at later time. The SenseInAir® will be followed by SenseInWater® and SenseInSoil® devices.

Stay tuned, in the next couple of posts, we will present SenseInAir® dashboard and will discuss sensors calibration and methods to obtain accurate data.

The Air Quality Index (AQI) is a number used mostly by government agencies to indicate the level of pollution to the general public. The AQI is also sometimes referred to as Air Pollution Index (API) or Air Quality Health Index (AQHI). As the AQI increases, it can have adverse health effects on a growing percentage of the population, depending on how worse the air quality gets. Most countries have their own way to calculate an AQI, mainly driven by national air quality standards. What you do see in common however is that they divide the AQI measured into ranges and color and label them so it’s easy for people to understand how much risk they run:

Now how does an AQI get calculated? Well, first of all you need to measure the levels of certain gasses as well as the level of particulates in the air over a certain period. The most common components that get measured and which are used to calculate an AQI are:

Ozone (O3): Ground level Ozone is not directly emitted by something, but is created by sunlight acting on NOx (Nitrogen Oxides) and VOC (Volatile Organic Compound) that exists in the air. Ozone is the primary component of smog and it can cause all kind of respiratory problems, even for instance for healthy people if they exercise under such conditions.

Sulfur Dioxide (SO2): SO2 is mainly formed by emissions from fossil fuels used by power plants and other industries, but also from large ships. If you breathe in SO2, it can irritate the nose, throat, and airways and creates a risk for people with respiratory problems.

Carbon Monoxide (CO): CO is emitted by combustion processes, when there is not enough oxygen for complete combustion. Concentrations of CO are mainly high in areas with large concentrations of cars, trucks etc. CO can cause reduction to the oxygen delivery to the body’s organs like the heart and brain. In large concentrations it can even cause dead.

Nitrogen Dioxide (NO2): NO2 is mainly formed by emissions from cars, buses, trucks, power plants etc., anything that burns fossil fuels. It contributes to respiratory problems as well as the buildup of smog, which both can seriously impact the human health.

Particulate Matter PM10: Also referred to as Dust Particles, has a size between 2.5 to 10 micrometer. These particles can be caused by grinding operations, dust stirred up by vehicles etc. Particle pollution can contribute to a broad range of health problems.

Particulate Matter PM2.5: Also referred to as Fine Particles, has a size of 2.5 micrometer or less. These particles can be caused by combustion processes, but also forest fires. Particle pollution can contribute to a broad range of health problems. These Fine Particles are more dangerous then Dust Particles as they are small enough to enter the blood vessels via the lungs.

To get the measurements for an AQI based on the above mentioned elements, governments often use large and expensive monitoring stations. Due to the cost it’s clear you can only have so many per city. It’s nice if you live close to one as then you have a good indication how healthy your living environment is. Wouldn’t it be nice however if there would be a way to increase the number of measuring stations by providing something smaller and more affordable, so that every community, street could have it’s own station and provide data to indicate to the neighborhood how safe it is, that’s what our next blog post will be about.